the act of a male individual shitting or pooping in the upper deck of the toilet while a girl goes down on you (aka; sucking your penis), while she releases poop out of her butthole into the lower deck bowl of the toilet.

Jeff to Randy: Dude, bro, Jerry definitely just got some of that double decker blumpkin action dome piece from that random B with the STDs.
Randy to Jeff: Real nice, real fuckin' nice.